Unitized spring device and master cylinder including such device

ABSTRACT

The invention is directed to improvements to the assembly of a unitized spring device. The spring device comprises a pair of retainer members which are tubular in shape and hollow inside. The retainer members have different outer circumference diameters which allow the second retainer member to fit onto the outer circumference of the first retainer member. The first retainer member has a first outward claw portion at one end and the second retainer member has a second inward claw portion at one end, such that the second claw portion can move beyond the first claw portion to couple the first and second retainer members in the axial direction. These first and second claw portions prevent one another from being pulled out in the coupled state. The first retainer member also comprises a slit which extends in the axial direction and divides at least the side having the first claw portion.

This application is a 371 of PCT/JP2004/008731 filed on Jun. 21, 2004,published on Jan. 6, 2005 under publication number WO 2005/001306 A1which claims priority benefits from Japanese Patent Application Number2003-183627 filed Jun. 26, 2003.

TECHNICAL FIELD

This invention relates to a unitized spring device that can be handledindependently, more specifically, to a spring device advantageouslyapplicable to a master cylinder for use in a vehicle's hydraulic brakingsystem or the like.

BACKGROUND ART

For example, a master cylinder for a vehicle includes a cylinder mainbody having a cylinder bore, a piston that defines a hydraulic chamberin the cylinder bore of the cylinder main body, and a spring device thatprovides the piston with the force of the spring. The elements of thespring device are a retainer member that restricts theexpansion/compression of the spring, and the spring supported by theretainer member.

In most spring devices, the piston itself serves as a direct springbearing for the spring, and therefore the spring device itself is notformed as a unit and cannot be handled independently. Various examplesof such conventional, non-unitized devices are disclosed by thefollowing documents.

Patent Document 1: Japanese Patent No. 3035228 that discloses a springdevice including a cup-shaped retainer, a screw member that has its oneend coupled to the retainer and its other end supported by a piston, anda spring supported between the retainer and the piston (see FIG. 1 inparticular).

Patent Document 2: U.S. Pat. No. 5,111,661 (that corresponds to JapanesePatent Laid-Open No. H03-109164) according to which an extended part ofthe piston plays the role of the spring member in the disclosure ofJapanese Patent No. 3035228 described above (see the part denoted byreference numeral 42 in FIG. 1 in particular).

Patent Document 3: Japanese National Publication No. 2002-535200 (thatcorresponds to Intentional Publication WO 00/44600) that discloses aspring device having a retainer arrangement in which a sleeve-shapedretainer member is coupled with a pin-shaped retainer member in atransverse direction deviated from the axial line, and a piston (26)serves as a spring bearing for a spring (38) (see FIG. 1 in particular)

Meanwhile, there is a known unitized spring device including a pair ofcoupled retainer members whose axial length is extensible/contractible,and a spring supported by these retainer members, and these elements canbe handled independently as a unit.

Patent Document 4: Japanese Utility Model Publication No. H05-13666discloses a spring device that includes a cup-shaped retainer, a rodmember having its one end coupled to the retainer and its other endhaving a spring bearing portion, and a spring supported between thespring bearing portion of the rod member and the retainer (see FIG. 3 inparticular). The spring device formed as a unit that can be handledindependently is more advantageous when it is assembled to the cylindermain body than those that are not formed as a unit.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

The inventers had studied about spring devices that are formed as aunit. (The term “unit” may be replaced by “cartridge ” or “package,”while the term “unit” is the most appropriate when a plurality ofelements are assembled and then the assembly can be handledindependently.) Consequently, it was found that with respect to aunitized spring device, there were needs for further improvements forthe assembly of the spring device itself, stable and smooth operationand reduction of disagreeable noise upon contacting. The conventionalretainer or retainer member in particular is generally made of a metaland can cause annoying noise when metal parts contact each other.

It is therefore an object of the invention to provide a technique offurther improving the assembly of a unitized spring device itself.

Another object of the invention is to provide a technique of making aunitized spring device operate smoothly and stably and reducingcontacting noise as much as possible.

Other objects of this invention will become clear from the followingdescription.

Means for Solving the Problems

According to the invention, a pair of retainer members supporting aspring is aligned in the axial direction, and pressing force acting inthe axial direction is applied to the retainer members in order toassemble them. In this way, the elements of the spring device can beassembled by a single motion. The spring device based on the concept isprincipally characterized as follows.

(A) Each of the pair of retainer members is tubular in shape and hollowinside, and on the outer circumference of a first retainer member havinga smaller diameter, a second retainer member having a larger diameter isfitted.

(B) The first retainer member has a first outward claw portion at oneend, the second retainer member has a second inward claw portion at oneend, the second claw portion can move beyond the first claw portion tocouple the first and second retainer members in the axial direction, andthese first and second claw portions function to prevent one anotherfrom being pulled out in the coupled state.

(C) The first retainer member includes a slit axially extending anddividing at least the side having the first claw portion.

The arrangement of the pair of retainer members fitted with one anotherin (A) is necessary for the axial length of these retainer member to beextended/shortened. In (A), not only the female-shaped, second retainermember but also the male-shaped, first retainer member is tubular inshape and hollow inside. This is advantageous in view of the readinessof coupling the retainer members as well as the reduction of the areaoccupied by the spring device (so that the volume of the hydraulicchamber in which the spring device is provided can be increased by thereduced volume). In view of the readiness, (A) in combination with (B)and (C) allows the first retainer member side having the smallerdiameter to elastically deform, so that the first and second retainermembers are coupled with each other.

It is clear from (B) that the retainer members both have a prescribedclaw portion at one end. The first and second claw portions at theretainer members allow the retainer members to move in the direction toreduce the axial length of the retainer members, while after theircoupling, the claw portions prevent each other from being pulled out andthus prevent the retainer members from being pulled out from each otherin the axial direction. In this way, the claw portions restrict themaximum axial length of the coupled retainer members.

Furthermore, (C) is a condition necessary for the first retainer memberhaving the smaller diameter and positioned on the inner circumferentialside to elastically deform when the first and second retainer membersare coupled. It is advantageous that at least the retainer member on theinner circumferential side is mainly elastically deformed because theretainer members can be coupled with each other substantially withoutelastically deforming the retainer member on the outer circumferentialside. In this way, the second retainer member positioned close to theinner circumference of the spring can be prevented from inadvertentlydeforming and contacting the spring during the operation of the springdevice.

The first and second claw portions in the first and second retainermembers may have various raised shape sections such as a semi-circularshape and a V shape, and at least one of the first and second clawportions preferably has a wedge-shaped section. In this way, when theretainer members are pressed against each other in the axial directionin order to couple them, the wedge-shaped claw portion quickly deformsthe more deformable retainer member on the inner circumferential side bythe boosting effect of the wedge, so that the coupling can be achievedby a single motion. More preferably, the first and second claw portionsmay both have a wedge shape. Note that the claw portions maycontinuously be provided entirely in the circumferential direction. (Theclaw portions are “continuous” in the first retainer member except forthe slits, because the first retainer member is divided by the slits inthe first place.) The claw portions may be provided in a plurality oflocations at intervals in the circumferential directions.

The first retainer member on the inner circumferential side may bedevised or have a particular structure so that the first retainer membermay more easily elastically deform. For example, it is advantageous thatthe thickness of the member on the side opposite to the side having thefirst claw portion is thinner, or a slit dividing the side having thefirst claw portion is extended to a position nearer to the springbearing portion on the end than the central position of the firstretainer member in the axial direction (for example to the vicinity ofthe base of the first retainer member).

Meanwhile, the second retainer member on the outer circumferential sidemay preferably have an outer diameter slightly larger on the sideopposite to the side having the second claw portion. In this way, aspring can easily be assembled to the members, and when the springextends/compresses, the spring and retainer members can be preventedfrom inadvertently contacting one another. When the pair of retainermembers is extended/shortened in the axial direction, at least one ofthe first and second claw portions on the end can guide thecircumferential wall of the corresponding retainer member.

The pair of retainer members is both preferably made of a resin materialin order to reduce contacting noise as much as possible. In that case,in order to reinforce the strength of the resin, it is more preferredthat reinforcement fiber such as glass fiber is mixed there into.

The spring device according to the invention may effectively be appliedas an inner part for use in various master cylinders for vehicles. Thedevice may be applied to master cylinders not only of a general tandemtype but also of a single type. When the device is applied to the tandemtype, it may be provided on the primary side and/or the secondary side.Application of the invention to a plunger type having a relief port or aconventional type particularly allows the master cylinder to be reducedin size, and the invention is also applicable to a center valve type.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a tandem type master cylinder taken alongthe axial line, showing the master cylinder having a spring deviceaccording to the invention incorporated therein;

FIG. 2 is a view of the spring device according to the invention beforethe device is incorporated in the master cylinder;

FIG. 3 is a sectional view of a second retainer member seen from thefront;

FIG. 4 is a side view of the second retainer member in FIG. 3 seen fromthe right in the sheet;

FIG. 5 is a sectional view of a first retainer member seen from thefront; and

FIG. 6 is a side view of the first retainer member in FIG. 5 seen fromthe right in the sheet.

DESCRIPTION OF REFERENCE CHARACTERS

-   10 master cylinder-   20 cylinder main body-   22 cylinder bore-   51, 52 spring device-   60 first retainer member-   70 second retainer member-   80 spring-   600, 700 tubular main body-   602 slit-   610 first claw portion-   630, 730 spring bearing portion-   720 second claw portion

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a tandem type, plunger shaped master cylinder according toone embodiment of the invention. The tandem type master cylinder 10includes a primary part 101 and a secondary part 102 independent fromeach other. In the shown embodiment, a spring device according to theinvention is incorporated in each of the parts 101 and 102.

Referring to FIG. 1, the general structure of the tandem type mastercylinder 10 will be disclosed. The outer part of the master cylinder 10is a cylinder main body 20 made of an aluminum alloy. The cylinder mainbody 20 has a boss portion 201 that supports a reservoir (not shown)thereabove, and a cylinder bore 22 inside that axially extends from anopen, first end 20 h to a closed, second end 20 b. The boss portion 201supports the reservoir storing a hydraulic fluid therein and the nippleof the reservoir is fitted and connected to the inside of the portion.

A secondary piston 32 is inserted deeply inside the cylinder bore 22 ofthe cylinder main body 20, and a primary piston 31 is placed near theopening of the cylinder bore 22. The secondary and primary pistons 32and 31 are aligned along the axial line of the cylinder bore 22. Theprimary piston 31 has a part inserted in the cylinder bore 22 and itsremaining part extended outwardly from the opening of the cylinder bore22. The extended part comes inside a booster that is not shown and isconnected with the booster. As is well known, the booster boosts theforce applied to a brake pedal, and applies the boosted force to themaster cylinder 10 (to the primary piston 31 of the master cylinder 10,to be exact).

The secondary and primary pistons 32 and 31 have recesses 321 and 322,and 311 and 312, respectively on both sides in the axial direction. Therecess 322 of the secondary piston 32 on the side of the second end 20 bserves as a space to receive a part of the spring device 52 on thesecondary side, and the recess 321 on the side of the first end 20 h onthe opposite side serves as a space to receive a part of the springdevice 51 on the primary side. The recess 312 on the side of the secondend 20 b of the primary piston 31 similarly serves as a space to receivea part of the spring device 51 on the primary side, while the recess 311on the side of the first end 20 h of the primary piston 31 serves as aspace to receive the output rod (not shown) of a booster separate fromthe spring device.

In this way, in the cylinder bore 22 of the cylinder main body 20, thereare the spring device 52 on the secondary side, the secondary piston 32,the spring device 51 on the primary side, and the primary piston 31arranged in alignment in this order in the axial direction from theinside of the bore toward the opening. The two chambers defined by thepistons 32 and 31, in other words, the part 42 having the spring device52 and the part 41 having the spring device 51 both serve as hydraulicchambers. Herein, the spring devices 52 and 51 on the secondary andprimary sides have substantially the same structure although the springforce is smaller on the secondary side than on the primary side.Therefore, the elements of the spring devices 52 and 51 will be denotedby the same reference characters in the following description.

FIG. 1 shows how the spring device 52 (51) is incorporated inside thecylinder bore 22 of the cylinder main body 20, and FIG. 2 shows thespring device 52 (51) before it is incorporated inside. The springdevice 52 (51) includes a pair of resin-molded retainer members 60 and70 and a spring (compression coil spring) 80 supported by the retainermembers. The retainer members 60 and 70 are both tubular in shape andhollow inside and the retainer member (second retainer member) 70 havingthe larger diameter is fitted on the outer circumference of the retainermember (first retainer member) 60 having the smaller diameter.Therefore, the first retainer member 60 as a male member and the secondretainer member 70 as a female member are coupled with each other.

The tubular, first and second retainer members 60 and 70 have clawportions 610 and 720 at the ends of the tubular main bodies 600 and 700on one side, and spring bearing portions 630 and 730 on the endsopposite to the claw portions 610 and 720. The spring bearing portions630 and 730 both have an outward flange shape in order to support theends of the spring 80. Meanwhile, the claw portion 610 of the firstretainer member 60 is radially outwardly shaped but the claw portion 720of the second retainer member 70 is radially inwardly shaped since thefirst and second retainer members 60 and 70 serve as the male and femalemembers, respectively. The first and second claw portions 610 and 720prevent one anther from being pulled out and restrict the maximum lengthof the spring 80.

As shown in FIG. 2, when the spring device 52 (51) is outside thecylinder bore 22 of the cylinder main body 20 (in other words, before itis incorporated into the cylinder bore 22), the first and second clawportions 610 and 720 abut against each other by the force of the spring80 supported between the spring bearing portions 630 and 730. In thisway, the spring device 52 (51) can be handled independently as a singleunit. In the spring device 52 (51) before it is incorporated, the clawportions 610 and 720 abut against each other, and therefore the force ofthe spring 80 is applied to the retainer members 60 and 70 through theclaw portions 610 and 720. Therefore, the materials of the retainermembers 60 and 70 must have enough strength for the state. In thisviewpoint, the materials of the retainers 60 and 70 may preferablyinclude fiber-reinforced resin such as polyamide resin containing 30%glass fiber (trade name: Nylon 66). In the spring device 52 (51) afterit is incorporated as shown in FIG. 1, however, pre-load is applied tothe spring 80, so that the first and second claw portions 610 and 720are separated from each other in the axial direction. Therefore, theforce of the spring 80 is applied only to the spring bearing portions630 and 730, not to the tubular main bodies 600 and 700 of the retainermembers 60 and 70. Consequently, the materials of the retainer members60 and 70 do not need strength more than necessary.

FIG. 3 is a sectional view of the female shaped, second retainer member70 seen from the front, and FIG. 4 is a side view of the second retainermember 70 in FIG. 3 seen from the right in the sheet. The main body 700of the second retainer member 70 has its axial ends opened, and a roundhole 702 and an elongate hole 703 provided at the main body 700penetrate between the inner side and the outer side of the main body700. Two such round holes 702 are provided near the second claw portion720 in the circumferential direction. As can be seen from FIG. 4, threesuch elongate holes 703 on the side of the spring bearing portion 730are provided in the circumferential direction. The main body 700 has aslightly thicker part on the side of the second claw portion 720, butthe thickness difference between the part and the side having the springbearing portion 730 is insignificant. Therefore, the main body 700 canbe considered to have a substantially equal thickness (for example inthe range from 0.5 mm to 0.65 mm) generally in the axial direction. Now,the shape of the second claw portion 720 at one end of the main body 700should be noted. The second claw portion 720 has a height of a littlemore than 1 mm and has a wedge shape (or V-shape) in a section. The face720 v on one side of the second claw portion 720 having the wedge shapedsection is orthogonal to the axial line of the main body 700, and theface 720 t on the other side is inclined by 30° to 40° with respect tothe face 720 v.

FIG. 5 is a sectional view of the male-shaped, first retainer member 60seen from the front, and FIG. 6 is a side view of the first retainermember 60 in FIG. 5 seen from the right in the sheet. The main body 600of the first retainer member 60 has its axial ends both opened. Theouter diameter of the main body 600 is smaller than that of the mainbody 700 of the second retainer member 70, so that the main body 600 isfitted in the inner circumference of the main body 700 with allowance.The main body 600 of the first retainer member 60 has a slit 602extending from the side having the first claw portion 610 to thevicinity of the base on the side having the spring bearing portion 630.As shown in FIG. 6, such slits 602 are provided in two locations 180°apart in the circumferential direction. The main body 600 of the firstretainer member 60 has a thickness generally larger than that of themain body 700 of the second retainer member 70, and the side having thefirst claw portion 610 is thicker than the side having the springbearing portion 630. The first claw portion 610 on one end of the mainbody 600 of the first retainer member 60 is formed outwardly, but hasthe same height and shape as those of the second claw portion 720. Morespecifically, the first claw portion 610 has a height slightly largerthan 1 mm, and a wedge-shaped (V-shaped) section. The wedge-shaped, oneface 610 v of the first claw portion 610 is orthogonal to the axial lineof the main body 600 and the other face 610 t is inclined by about 30°to 40° with respect to the face 610 v. Note that a recess 605 that is90° apart from the slit 602 in the circumferential direction serves as agate for resin molding.

Now, referring to FIG. 6, the shape of the part having the first clawportion 610 of the main body 600 will be described. When an end of themain body 600 is viewed in the axial direction, the two slits 602 arealigned and the outer diameters of the first retainer member 60 in thelocations of these slits are smaller than the outer diameter of theother part without the slits 602. The outer circumferential part of theend is partly cut in order to reduce the outer diameter for thefollowing reason. When the male-shaped, first retainer member 60 and thefemale-shaped, second retainer member 70 are assembled, the first clawportion 610 and the second claw portion 720 of these members arearranged to oppose each other, and the retainer members 60 and 70 areprovided with force in the axial direction. In this way, the forcetransmitted through the claw portions 610 and 720 causes the main body600 of the first retainer member 60 (that is easily deformable becauseof the slit 602) to elastically deform to narrow the opening side of theslit 602. The deformation tends to increase the outer diameter of theend of the main body 600 on the side facing the opening of the slit 602.For example, if the main body 600 is in the circular shape without beingpartly cut in the end, the circle could deform into an ellipse, whichcan prevent the first claw portion 610 from being smoothly fitted in theinner circumference of the second claw portion 720. The outercircumferential part of the end of the main body 600 is partly cut inorder to eliminate the possibility. When the first and second retainermembers 60 and 70 are assembled, one of the retainer members (normallythe second retainer member 70 having the larger outer diameter) isprovided with the spring 80, and the force in the axial direction asdescribed above is applied, so that these retainer member 60 and 70 maybe coupled to be assembled by a single motion. This is because theeffect of the wedge shape of the first and second claw portions 610 and720 allows the main body 600 of the easily deformable first retainermember 60 to be readily deformed. Once the assembling is over, the firstand second claw portions 610 and 720 can prevent one another from beingpulled out, so that the spring device 51 (52) can maintain its form as aunit as shown in FIG. 2.

As an inner part of the master cylinder 10, the spring device 51 (52)smoothly and quietly extends and compresses the spring 80 as the firstclaw portion 610 or/and the second claw portion 720 guide thecorresponding one of the circumferential walls of the main bodies 700and 600 of the retainer members 70 and 60 during the operation of themaster cylinder 10. In this respect, since the retainer members 60 and70 are made of a resin material, the sound caused by contacting is smalland not annoying. Since the two retainer members 60 and 70 are made ofthe same resin material, troubles caused by changes in the size of theretainer members 60 and 70 according to the temperature and humiditychanges can be prevented.

1. A spring device comprising a pair of retainer members coupled so thattheir axial length can be increased/reduced and a spring supported bythese retainer members, said elements being formed into a unit that canbe handled independently, wherein (A) each of said pair of retainermembers is tubular in shape and hollow inside, and on the outercircumference of a first retainer member having a smaller diameter, asecond retainer member having a larger diameter is fitted; (B) saidfirst retainer member has a first outward claw portion at one end, saidsecond retainer member has a second inward claw portion at one end, thesecond claw portion can move beyond the first claw portion to couple thefirst and second retainer members in the axial direction, and thesefirst and second claw portions function to prevent one another frombeing pulled out in the coupled state; and (C) said first retainermember includes plural slits axially extending and dividing at least theside having said first claw portion, and thereby said first retainermember on the inner circumferential side is elastically deformed whensaid first and second retainer members are pressed against each other inthe axial direction in order to couple them.
 2. The spring deviceaccording to claim 1, wherein at least one of said first and second clawportions has a wedge-shaped section.
 3. The spring device according toclaim 1, wherein said first retainer member is thinner on the sideopposite to the side having said first claw portion.
 4. The springdevice according to claim 1, wherein said second retainer member has anouter diameter that is larger on the side opposite to the side havingsaid second claw portion.
 5. The spring device according to claim 1,wherein when said pair of retainer members extends/compresses in theaxial direction, at least one of said first and second claw portionsguides the circumferential wall of the corresponding one of the retainermembers.
 6. The spring device according to claim 1, wherein said firstand second retainer members both comprise a spring bearing portion tosupport an end of said spring on the side opposite to the side havingthe claw portion.
 7. The spring device according to claim 6, wherein theslit in said first retainer member has one end that divides the sidehaving said first claw portion and the other end that is positionedcloser to said spring bearing portion than the central position of thefirst retainer member in the axial direction.
 8. The spring deviceaccording to claim 1, wherein when the side of said first retainermember having said first claw portion is viewed in the axial direction,two said slits are aligned in the radial direction, and the outerdiameter of the first retainer member in the locations of the slits issmaller than the outer diameter of the other part without said slits. 9.The spring device according to claim 1, wherein said first and secondretainer members are both made of a resin material.
 10. A mastercylinder comprising a cylinder main body having a cylinder bore, apiston that defines a hydraulic chamber in the cylinder bore of cylinderthe main body, and a spring device providing the piston with springforce, said spring device comprising a pair of retainer members coupledto one another so that the axial length of the members can beincreased/reduced, and a spring supported by these retainer members,said spring device being formed as a unit that can be handledindependently, wherein said spring device is further characterized inthat (A) each of said pair of retainer members is tubular in shape andhollow inside, and on the outer circumference of a first retainer memberhaving a smaller diameter, a second retainer member having a largerdiameter is fitted; (B) said first retainer member has a first outwardclaw portion at one end, said second retainer member has a second inwardclaw portion at one end, the second claw portion can move beyond thefirst claw portion to couple the first and second retainer members inthe axial direction, and these first and second claw portions functionto prevent one another from being pulled out in the coupled state; and(C) said first retainer member includes plural slits axially extendingand dividing at least the side having said first claw portion, andthereby said first retainer member on the inner circumferential side iselastically deformed when said first and second retainer members arepressed against each other in the axial direction in order to couplethem.
 11. The master cylinder according to claim 10, wherein at leastone of said first and second claw portions has a wedge-shaped section.12. The master cylinder according to claim 10, wherein said first andsecond retainer members are both made of a resin material.